The present invention relates to a manufacturing method of a piezoelectric vibrator having a piezoelectric vibration piece hermetically sealed by lid members, and more particularly to a manufacturing method of a piezoelectric vibrator using anodic bonding.
As shown in FIG. 7, a conventional surface-mount type piezoelectric vibrator 50 is comprised of a piezoelectric vibrator piece 51, a container 52 fixing one end of the piezoelectric vibration piece 51, and a lid member 56 for sealing the container 52.
The container 52 fixed with the piezoelectric vibration piece 51 has a concave portion 53 defining a space sufficiently large to an extent not interfering with vibration of the piezoelectric vibration piece 51. In this concave portion 53 a step portion 54 is provided having a smaller depth than other portions. The piezoelectric vibration piece 51 is fixed on a top surface of the step portion 54 of the container 52 through an adhesive layer 55, such as a solder material or conductive adhesive. The container 52 is bonded thereon with the lid member 56 through a similar adhesive layer 55 used for fixing of the piezoelectric vibration piece 51, thus hermetically sealing the piezoelectric vibration piece 51 within the concave portion 53 of the container 52.
However, where a solder material is used as an adhesive layer 55 to bond the piezoelectric vibration piece 51 and the lid member 56, bonding is made by thermally fusing the solder member and accordingly gas is produced due to the fusing. Because the gas will be filled within the hermetically-sealed concave recess 53 of the container 52, there is the problem that an electrode film of the piezoelectric vibration piece 51 causes chemical change such as oxidation thus having an effect upon reliability of the piezoelectric vibrator.
Meanwhile, where a conductive adhesive is used as an adhesive layer 55, gas is produced due to an epoxy resin upon thermosetting thus resulting in a problem having a bad effect upon the piezoelectric vibration piece similarly to the solder material.
Furthermore, there is a possibility that such a gas occurs to heating in mounting process, particularly in a reflow process or during environmental testing, after completing production of a piezoelectric vibrator.
The present invention has been made in view of such a circumstance, and it is an object to provide a manufacturing method of a piezoelectric vibrator which is free from lowering of piezoelectric vibrator characteristic.
A first aspect of the present invention for solving the above problem lies in, in a manufacturing method of a piezoelectric vibrator having a piezoelectric vibration plate having a piezoelectric vibration piece and a frame portion integrally connected with a base portion thereof and surrounding the piezoelectric vibration piece, on respective sides of which a pair of lid members are bonded to hermetically seal the piezoelectric vibration piece without interfering with vibration of the piezoelectric vibration piece, the manufacturing method of the piezoelectric vibrator comprising a step of: forming a metal film generally over an entire surfaces of respective surfaces of the piezoelectric vibration plate; patterning the metal film to form oscillation electrode films on both surfaces of the piezoelectric vibration piece and forming bonding films to be bonded to the pair of lid members in a corresponding area to the both surfaces of the frame portion; and laminating the piezoelectric vibration plate and the pair of lid members through the bonding films on both surfaces of the frame portion of the piezoelectric vibration plate by applying a temperature of 100-200xc2x0 C. and applying a voltage of 0.5-5.0 kV to the lid members and the bonding films with the piezoelectric vibration plate side rendered as an anode.
A second aspect of the invention lies, in that in the first aspect, the lid members are formed of soda-lime glass and the metal film is formed of an aluminum alloy.
In the above invention, it is possible to form a piezoelectric vibration plate and lid members through a bonding film positively and easily.